CN103098383B - Systems and methods for PUCCH subband feedback signaling in wireless networks - Google Patents

Abstract

A mobile station for use in a wireless network. The mobile station sends a feedback report to a base station of the wireless network. The feedback reports include a first feedback report, a second feedback report, and a third feedback report. The first feedback report includes a Precoder Type Indication (PTI) value indicating at least one of a period of the second feedback report and a period of the third feedback report. The PTI value indicates a ratio of a period of the second feedback report and a period of the third feedback report. The PTI value further indicates selected feedback information included in the second feedback report and the third feedback report.

Description

Systems and methods for PUCCH subband feedback signaling in wireless networks

technical field

The present application relates generally to wireless networks, and more particularly to feedback signaling for Physical Uplink Control Channel (PUCCH) subbands in Long Term Evolution-Advanced (LTE-A) wireless systems.

Background technique

In 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), Orthogonal Frequency Division Multiplexing (OFDM) is adopted as a downlink (DL) transmission scheme.

The 3GPP LTE (Long Term Evolution, Long Term Evolution) standard is the final stage in the realization of true fourth generation (4G) mobile phone networks. Most of the major mobile operators in the US and some global operators have announced plans to convert their networks to LTE starting in 2009. LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS). Much of 3GPP Release 8 focuses on adopting 4G mobile communication technologies, including an all-IP flat networking architecture.

The 3GPP LTE standard uses Orthogonal Frequency Division Multiplexing (OFDM) for the downlink (ie, from the base station to the mobile station). Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier transmission technique that transmits on many orthogonal frequencies (or subcarriers). Orthogonal subcarriers are modulated separately and separated in frequency so that they do not interfere with each other. This provides high spectral efficiency and resistance to multipath effects.

The descriptions of the following documents and standards are incorporated herein as if fully set forth herein: 1) Document No. R1-101683, "WayForwardForRel-10FeedbackFramework", February 2010; 2) Document No. R1-102579, "WayForwardOnRelease10Feedback", RANWG1, April 2010; 3) Document No. R1-103419, "WayForwardonCSIFeedbackDesignForRel-10LDMIMO", May 2010; 4) Document No. R1-103332, "WayForwardonUEFeedback", May 2010; 5) Document No. R1-103333, "Refinements of FeedbackAndCodebook Design", May 2010; 6) Document No. R1-103805, "DoubleCodebookPerformanceEvaluation", June 2010; 7) Document No. R1-103701, "8TxCodebookDesign", June 2010; and 8) 3GPP Technical Specification No. 36.211.

In Release 10 LTE system, the mobile station (or user equipment) performs the feedback of precoding matrix index (PMI), rank indicator (RI) and channel quality indicator (CQI) to the base station (or eNodeB). In the 3GPPRAN1#60 meeting, the development direction for feedback in Release 10 was agreed. Release 10 employs implicit feedback of Precoding Matrix Index (PMI), Rank Indicator (RI) and Channel Quality Indicator (CQI). The user equipment (UE) or mobile station (MS) spatial feedback for the subbands represents the precoder, and the CQI is calculated based on the assumption that on each subband in the CQI reference resource, the eNodeB or base station (BS) uses The specific precoder (or precoders) as given by the feedback. Notably, a subband may correspond to the entire system bandwidth.

The subband precoder consists of two matrices. The precoder structure is applied to all transmit (Tx) antenna array configurations. Each of the two matrices belongs to a separate codebook. At both the base station (eNodeB) and the mobile station (user equipment) the codebook is known (or synchronized). The codebook may or may not change over time for different subbands. Together, the two codebook indices determine the precoder. One of the two matrices addresses broadband or long-term channel characteristics. Another matrix addresses frequency selection or short-term channel characteristics. It should be noted that the matrix codebook in this context should be interpreted as the matrix for each resource block (RB) known to both the mobile station (or UE) and the base station (or eNodeB) A finite enumerated set of . It should also be noted that Release 8 precoder feedback may be considered a special case of this structure.

Two messages are transmitted in the following manner: 1) Rel-10 feedback will be based on implicit feedback similar to Rel-8 feedback; and 2) 2 codebook indices will specify the precoder in Rel-10, where one codebook for wideband and/or long-term channel characteristics, and another codebook for frequency selection and/or short-term channel characteristics.

In the RAN1#60bis meeting, another development direction for the mobile station (or UE) feedback in Rel-10 was also agreed. The precoder W for a subband is a function of two matrices, W1 and W2 (ie, where W1 ∈ C1 and W2 ∈ C2 ). In this disclosure, W1 is also referred to as a first PMI, and W2 is also referred to as a second PMI. Codebooks C1 and C2 are codebook 1 and codebook 2, respectively. The first PMI targets wideband (or long-term) channel characteristics. The second PMI is for frequency selective (or short-term) channel characteristics. For the Physical Uplink Control Channel (PUCCH), unless the payload is too large to send the first PMI and the second PMI in the same subframe on the PUCCH, the feedback corresponding to the first PMI and the second PMI can be in or in the same subframe. In addition, periodic and occasional reports are separate.

Therefore, there are important differences in feedback between Release 8 (Rel-8) and Release 10 (Rel-10) of 3GPP networks. In Release 8, only one codebook index specifies a precoder. However, in Release 10, two codebook indices specify a precoder. In addition, the two codebook indices in Rel-10 may also be sent in different subframes or in the same subframe.

In the RAN1#62bis meeting, a development direction for the signaling of physical uplink control channel (PUCCH) subband feedback was agreed. Specifically, three PUCCH feedback modes are agreed upon with two (2) candidates for the extension of Rel-8 PUCCH Mode 1-1 and one (1) candidate for the extension of Rel-8 PUCCH Mode 2-1.

More specifically, candidates for PUCCH subband feedback (extension of PUCCH mode 2-1 of Rel-8) are as follows. The precoder W for the subband is determined from the 3-subframe report conditional on the latest rank indicator (RI) report. The report format includes 3 reports. Report 1 includes RI and 1-bit Precoder Type Indication (PTI). In report 2, if PTI=0, report W1. If PTI=1, report wideband CQI and wideband W2. In report 3, if PTI=0, wideband CQI and wideband W2 are reported. If PTI=1, subband CQI and subband W2 are reported. For 2 and 4 transmit (TS) antennas, it is assumed that the PTI value is set to 1 and it is not signaled.

Contents of the invention

[technical problem]

Therefore, there is a need in the art for improved apparatus and methods for providing feedback information related to CQI, PMI and RI in Rel-10 wireless networks. In particular, there is a need in the art for improved means for providing feedback information related to CQI, PMI and RI in a wireless network of Rel-10 that minimizes signaling overhead while improving the granularity of the feedback information and method.

[Solution to problem]

A mobile station is provided for use in a wireless network. The mobile station sends feedback reports to the base station of the wireless network. The feedback reports include a first feedback report, a second feedback report and a third feedback report. The first feedback report includes a precoder type indication (PTI) value. The PTI value indicates at least one of a period of the second feedback report and a period of the third feedback report. In an advantageous embodiment, the PTI value represents the ratio of the second feedback reporting period to the third feedback reporting period.

The second feedback report and the third feedback report include selected feedback information including at least one of wideband feedback information and subband feedback information. In an advantageous embodiment, the PTI value also represents selected feedback information.

A mobile station is provided for use in a wireless network. A mobile station is operable to communicate with a base station that transmits using a precoder specified by a codebook. The mobile station performs rank-dependent codebook subset selection for subband W2 feedback such that when the mobile station sends a first precoder type indicator (PTI) value, the mobile station uses the first subband W2 codebook to The base station transmits, and when the mobile station transmits the second PTI value, the mobile station transmits to the base station using the second subband W2 codebook. The codebook for the second subband W2 is a subset of the codebook for the first subband W2.

Before beginning the detailed description of the present invention below, it is instructive to set forth definitions of certain words and phrases used throughout this patent document: The terms "comprises" and "comprises", and their derivatives mean without limitation includes; the term "or" is inclusive, meaning and/or; the phrases "associated with" and "associated with", and their derivatives may mean including, included, interrelated with connect, contain, be included, connect to or be connected with, combine to or combine with, communicate with, cooperate with, interweave, juxtapose, approach, be bound to or with, have, have The properties of ... etc. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to the terms preceding such defined words and phrases. and future use.

Description of drawings

For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which like numerals indicate like parts:

1 illustrates an exemplary wireless network performing feedback for a Physical Uplink Control Channel (PUCCH) in accordance with the principles of the present disclosure;

Figure 2 illustrates a base station communicating with a plurality of mobile stations according to an embodiment of the disclosure;

FIG. 3 illustrates a 4×4 multiple-input multiple-output (MIMO) system according to an embodiment of the present disclosure;

Figure 4 shows a feedback report with a precoder type indicator (PTI) value of 0;

Figure 5 shows a feedback report with a precoder type indicator (PTI) value of 1;

Figure 6 shows a modified feedback report for a precoder type indicator (PTI) value of 1 in a first alternative embodiment;

Figure 7 shows a modified feedback report for a precoder type indicator (PTI) value of 1 in a second alternative embodiment;

Figure 8 shows a modified feedback report for a precoder type indicator (PTI) value of 1 in a third alternative embodiment;

Figure 9 shows a modified feedback report for a precoder type indicator (PTI) value of 1 in which four report types are used;

FIG. 10 shows an example of subband reporting for subband CQI/W2 reporting according to the first alternative embodiment of the present disclosure;

FIG. 11 shows a subband reporting example for subband CQI/W2 reporting according to a second alternative embodiment of the present disclosure; and

Fig. 12 shows an example of subband reporting for subband CQI/W2 reporting according to a third alternative embodiment of the present disclosure.

Detailed ways

1 through 12, discussed below, and the various embodiments used to describe the principles of the invention in this patent document are by way of illustration only and should not be construed to limit the scope of the invention in any way. Those skilled in the art will understand that the principles of the invention may be implemented in any suitably arranged wireless network.

1 illustrates an example wireless network 100 that performs feedback for a Physical Uplink Control Channel (PUCCH) in accordance with the principles of the present disclosure. Wireless network 100 includes base station (BS) 101, base station (BS) 102, base station (BS) 103, and other similar base stations (not shown). Base station 101 communicates with the Internet 130 or similar IP-based network (not shown).

Depending on the type of network, other well-known terms such as "eNodeB", "eNB" or "access point" may be used instead of "base station". For convenience, the term "base station" shall be used herein to refer to a network infrastructure component that provides wireless access to remote terminals.

The base station 102 provides wireless broadband access to the Internet 130 to a first plurality of mobile stations within the coverage area 120 of the base station 102 . The first plurality of subscriber stations includes: mobile station 111, which may be located in a small business (SB); mobile station 112, which may be located in an enterprise (E); mobile station 113, which may be located in a WiFi hotspot (HS); Station 114, which may be located in a first residence (R); mobile station 115, which may be located in a second residence (R); and mobile station 116, which may be a mobile device (M), such as a cell phone, wireless laptop, Wireless PDA, etc.

For convenience, the term "mobile station" is used herein to denote any remote wireless device that wirelessly accesses a base station, regardless of whether the mobile station is a true mobile device (e.g., a cell phone) or is generally considered a fixed Devices (for example, desktop personal computers, vending machines, etc.). In other systems, other well-known terms such as "subscriber station (SS)", "remote terminal (RT)", "wireless terminal (WT)", "user equipment (UE)", etc. may be used instead of "mobile station ".

Base station 103 provides wireless broadband access to Internet 130 to a second plurality of base stations within coverage area 125 of base station 103 . The second plurality of mobile stations includes mobile station 115 and mobile station 116 . In an exemplary embodiment, base stations 101-103 may communicate with each other and with mobile stations 111-116 using OFDM or OFDMA techniques.

Although only six mobile stations are depicted in FIG. 1, it should be understood that wireless network 100 may provide wireless broadband access to additional mobile stations. Notably, mobile station 115 and mobile station 116 are located on the edge of both coverage area 120 and coverage area 125 . Each of mobile station 115 and mobile station 116 communicates with both base station 102 and base station 103 and, as is known to those skilled in the art, may be considered to operate in a handover mode.

An example description of a closed-loop transmit beamforming scheme based on a codebook design can be found in the following papers: 1) "Grassmannian Beamforming For Multiple-Input, Multiple-Output Wireless Systems," by D. Love, J. Heath, and T. Strohmer, "IEEE Transactions on Information Theory, 2003 and 2) "Near-Optimal Codebook Constructions For Limited Feedback Beamforming In Correlated MIMO Channels With Few Antennas," IEEE2006 International Symposium on Information Theory by V. Raghavan, A.M. Sayeed, and N. Boston. Both documents are hereby incorporated by reference as if fully set forth herein.

In the case where the base station forms a transmit antenna beam toward a single user, or forms transmit antenna beams toward multiple users at the same time and at a certain frequency, closed-loop codebook-based transmit beamforming can be used. An exemplary description of such a system can be found in Quentin H. Spencer, Christian B. Peel, A. Lee Swindlehurst, and Martin Harrdt, "An Introduction To the Multi-User MIMO Downlink," IEEE Communication Magazine, October 2004, which is hereby incorporated by reference , as it is fully elaborated in this paper.

A codebook is a predetermined set of antenna beams known to the mobile station. Codebook-based precoding MIMO can provide significant spectral efficiency gains in downlink closed-loop MIMO. In the IEEE802.16e and 3GPP LTE standards, limited feedback based on four transmit (4-TX) antennas in a closed-loop MIMO configuration is supported. In IEEE802.16m and 3GPP LTE-Advanced standards, in order to provide peak spectrum efficiency, an eight-transmit (8-TX) antenna configuration is proposed as a prominent precoding closed-loop MIMO downlink system. An exemplary description of such a system can be found in 3GPP Technical Specification No. 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA): Physical Channel and Modulation", which is hereby incorporated by reference as if fully set forth herein.

In order to eliminate the need for phase alignment processing in cases where channel sounding signals or common pilot signals (or midamble codes) are not used for data demodulation purposes, closed-loop transformed codebook-based transmit beamforming can be used. An exemplary description of such a system can be found in IEEEEC 802.16m-08/1345r2, "Transformation Method For Codebook Based Precoding" November 2008, which is hereby incorporated by reference as if fully set forth herein. The transformed codebook approach exploits channel correlation information to enhance the performance of standard codebooks, especially in highly correlated channels, and eliminates the need for phase alignment between multiple transmit antennas. Typically, channel-related information is based on second-order statistics and thus changes very slowly, similar to long-term channel effects such as shadowing and path loss. Therefore, the feedback overhead and computational complexity of utilizing relevant information is very small.

2 illustrates a view 200 of a base station 220 in communication with a plurality of mobile stations 202, 204, 206, and 208, according to an embodiment of the disclosure. Base station 220 and mobile stations 202, 204, 206, and 208 employ multiple antennas for transmitting and receiving radio wave signals. The radio wave signal may be an Orthogonal Frequency Division Multiplexing (OFDM) signal.

In FIG. 2, base station 220 performs simultaneous beamforming for each mobile station through multiple transmitters. For example, base station 220 transmits data to mobile station 202 via beamformed signal 210; transmits data to mobile station 204 via beamformed signal 212; transmits data to mobile station 406 via beamformed signal 214; and transmits data via beamformed signal 216 to Data is sent 408 to the mobile station. In some embodiments, base station 220 may perform beamforming for mobile stations 202, 204, 206, and 208 simultaneously. Each beamforming signal may be formed towards its intended mobile station at the same time and at the same frequency. For purposes of clarity, communication from a base station to a mobile station may also be referred to as downlink communication, and communication from a mobile station to a base station may also be referred to as uplink communication.

Base station 220 and mobile stations 202, 204, 206, and 208 employ multiple antennas for transmitting and receiving wireless signals. It should be understood that the wireless signal may be a radio wave signal and that the wireless signal may use any transmission scheme known to those skilled in the art, including an Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme.

Mobile stations 202, 204, 206, and 208 may be any device capable of receiving wireless signals. Examples of mobile stations 202, 204, 206, and 208 include, but are not limited to, personal data assistants (PDAs), laptop computers, mobile phones, handheld devices, or any other device capable of receiving beamforming transmissions.

OFDM transmission schemes are used to multiplex data in the frequency domain. Modulation symbols are carried on frequency subcarriers. Symbols modulated by Quadrature Amplitude Modulation (QAM) are serial-to-parallel converted and input to an Inverse Fast Fourier Transform (IFFT). At the output of the IFFT, N time domain samples are obtained. Here, N refers to the size of the IFFT/Fast Fourier Transform (FFT) used by the OFDM system. The signal after IFFT is parallel-serial converted, and a cyclic prefix (CP) is added to the signal sequence. CP is added to each OFDM symbol to avoid or mitigate the effects due to multipath fading. The resulting sequence of samples is called an OFDM symbol with CP. On the receiver side, assuming perfect time and frequency synchronization is achieved, the receiver first removes the CP and the signal is serial-to-parallel converted before being fed into the FFT. The output of the FFT is parallel-serial converted, and the resulting QAM modulation symbols are input to a QAM demodulator.

The total bandwidth in an OFDM system is divided into narrowband frequency units called subcarriers. The number of subcarriers is equal to the size N of the FFT/IFFT used in the system. In general, the number of subcarriers used for data is less than N because some subcarriers at the edge of the spectrum are reserved as safety subcarriers. In general, no information is sent on safe subcarriers.

Since each OFDM symbol has a finite duration in the time domain, the subcarriers overlap each other in the frequency domain. However, assuming perfect frequency synchronization of the transmitter and receiver, orthogonality is maintained at the sampling frequency. In case of frequency offset due to imperfect frequency synchronization or high mobility, the orthogonality of the subcarriers at the sampling frequency is broken, resulting in inter-carrier interference (ICI).

The use of multiple transmit antennas and multiple receive antennas at both a base station and a single mobile station in order to increase the capacity and reliability of a wireless communication channel is known as a single-user multiple-input multiple-output (SU-MIMO) system. MIMO systems provide a linear increase in capability with K, where K is the minimum number of transmit antennas (M) and receive antennas (N) (ie, K=min(M,N)). MIMO systems can be implemented using schemes of spatial multiplexing, transmit and receive beamforming, or transmit and receive diversity.

FIG. 3 illustrates a 4×4 multiple-input multiple-output (MIMO) system 300 according to an embodiment of the disclosure. In this example, four different data streams 302 are transmitted separately using four transmit antennas 304 . The transmitted signals are received at the four receive antennas 306 and interpreted as received signals 308 . Some form of spatial signal processing 310 is performed on the received signal 308 to recover the four data streams 312 .

An example of spatial signal processing is Vertical-Bell Laboratories Layered Space-Time (V-BLAST), which uses successive interference cancellation principles to recover the transmitted data stream. Other variants of MIMO schemes include schemes that perform some kind of space-time coding (eg, Diagonal Bell Labs Layered Space-Time (D-BLAST) ) on the transmit antennas. In addition, MIMO technology can be implemented using a transmit and receive diversity scheme, and a transmit and receive beamforming scheme to improve reliability of a link or system capacity in a wireless communication system.

In Channel State Indicator (CSI) Mode 1, depending on the value of Precoder Type Indication (PTI), an extension of PUCCH Mode 2-1 (i.e., subband feedback mode) allows multiplexing subbands in the same feedback mode. Both band feedback and broadband feedback. More specifically, when PTI=0, both report 2 and report 3 are wideband reports, and when PTI=1, report 2 is a wideband report and report 3 is a subband report. When PTI=0, since both report 2 and report 3 are broadband, naturally the feedback periodicity of report 2 and report 3 is similar. However, when PTI=1, report 3 is a subband report, which means that the feedback periodicity of report 3 should be smaller than that of report 2.

Let _NP2 be the period of report 2, and let _NP3 be the period of report 3. By way of example, the periodic unit of two reports may be a subframe. but:

H=N _P2 /N _P3 +1,

where N _P2 /N _P3 is the ratio between the period of report 2 and the period of report 3. It is worth noting that the period ratio depends on the PTI value. Therefore, in an advantageous embodiment of the invention, the value of H depends on the value of PTI. For example, when PTI=0, H=2 or 3, and when PTI=1, H=J*K+1, where J is the number of bandwidth parts, and K is a constant, which can be derived from The base station (eNB) signals K. In another example, when PTI=0, the value of H may be signaled by higher layers, and when PTI=1, then H=J*K+1, where J is the number of bandwidth parts, and K is Constant, K can be signaled from the base station (eNB) using higher layer signaling.

Such that N _P1 is the period to report 1, then:

M=N _P1 /N _P2 .

In an advantageous embodiment of the invention, the value of M also depends on the value of PTI. Also, let M ⁰ and H ⁰ be the period ratio when PTI=0, and let M ¹ and H ¹ be the period ratio when PTI=1. Then the following conditions among the four quantities hold:

H ⁰ *M ⁰ =H ¹ *M ¹ .

For this particular example, assume a total system bandwidth of 10MHz. Therefore, J=3 bandwidth parts (BP). If K=1, then H ¹ =4. If M ¹ =2, then H ¹ *M ¹ =4*2=8=H ⁰ *M ⁰ =2*4.

In some embodiments of the present disclosure, the exact values of H and/or M may be signaled using higher layer signaling.

In Figure 4 and Figure 5, the feedback reporting from the Mobile Station (MS) to the Base Station (BS) can be seen more clearly.

Figure 4 shows a feedback report with a precoder type indicator (PTI) value of 0. In FIG. 4, H ⁰ =2 and M ⁰ =4. Messages 401a and 401b are examples of Report 1, which contains a rank indicator (RI) and a PTI value=0 of 1 bit. Messages 402a, 402b, 402c, and 402d are examples of Report 2, which contains the precoder matrix value W1 (also called "first PMI"). Messages 403a, 403b, 403c, and 403d are examples of Report 3, which contain wideband precoder matrix values (WBW2) and wideband channel quality indicator (WBCQI) values.

So for every instance of report 1, there are 4 instances of report 2 and 4 instances of report 3 (i.e. M=4, since report 1 has 4 times the period of report 2). Also, for every instance of report 2, there is one instance of report 3 (i.e. H = 2, since the period of report 2 is equal to the period of report 3).

FIG. 5 shows a feedback report with a precoder type indicator (PTI) value of 1. In FIG. 5 , H ¹ =4 and M ¹ =2. Messages 501a and 501b are examples of Report 1, which contains a rank indicator (RI) and a 1-bit PTI value=1. Messages 502a and 502b are examples of Report 2, which include wideband precoder matrix values WBW2 and WBCQI values. Messages 503a, 503b, and 503c are examples of Report 3, which include a subband precoder matrix value SBW2 and a subband channel quality indicator (SBCQI) value.

So for every instance of report 1, there are 2 instances of report 2 and 6 instances of report 3 (i.e. M=2, since report 1 has 2 times the period of report 2). Also, for every instance of report 2, there are 3 instances of report 3 (ie H = 4, since the period of report 2 is 3 times that of report 3).

In this example, when PTI=1, no feedback information related to W1 is reported after the rank report. This means that in order to perform subband-based feedback, the mobile station may first feed back PTI=0. However, during the next RI feedback, the mobile station ensures to report the same W1 in the previous subframe. Otherwise, the mobile station should not perform subband feedback. This may limit the scheduling flexibility in the base station and may increase the complexity of the mobile station.

In an advantageous embodiment of the invention, the wideband feedback information is sent in a feedback report (Report 2) following Report 1, where PTI=1.

In a first alternative embodiment (ALT1), W1 information is reported together with wideband W2 and wideband CQI in report 2 when PTI=1. Therefore, Report 1 includes RI and 1 bit of Precoder Type Indication (PTI). In report 2, if PTI=0, report W1. If PTI=1, report W1, wideband CQI and wideband W2. In report 3, if PTI=0, wideband CQI and wideband W2 are reported. If PTI=1, subband CQI and subband W2 are reported. A first alternative embodiment is depicted in FIG. 6 .

Figure 6 shows a modified feedback report with a precoder type indicator (PTI) value of 1 in a first alternative embodiment. In FIG. 6, H ¹ =4 and M ¹ =2. Figure 6 is similar to Figure 5 in many respects. Messages 501a and 501b are examples of Report 1, which includes a rank indicator (RI) and a 1-bit PTI value=1. Similarly, messages 503a, 503b, and 503c are examples of report 3, which includes a subband precoder matrix value SBW2 and a subband channel quality indicator (SBCQI) value. However, messages 601a and 601b are new. Messages 601a and 601b are examples of report 2. Since PTI=1, messages 601a and 601b include wideband W1, wideband W2 and wideband CQI.

Furthermore, in order to limit the maximum payload size of Report 2 to 11 bits, codebook subset selection (codebook subsampling) is performed for the codebook of W1 book and/or the codebook of W2. Therefore, conditional on the value of PTI, the codebook of W1 can be sub-sampled or not. If PTI=0, then C1 (the codebook of W1) is not sub-sampled (codebook subset selection is not applied to C1). If PTI=1, then C1 (the codebook of W1) is sub-sampled (codebook subset selection is applied to C1).

In a second alternative embodiment (ALT2), W1 information is reported together with the wideband CQI in report 2 when PTI=1. Therefore, Report 1 includes RI and 1 bit of Precoder Type Indication (PTI). In report 2, if PTI=0, report W1. If PTI=1, report W1 and wideband CQI. In report 3, if PTI=0, wideband CQI and wideband W2 are reported. If PTI=1, subband CQI and subband W2 are reported. A second alternative embodiment is depicted in FIG. 7 .

Figure 7 shows a modified feedback report with a precoder type indicator (PTI) value of 1 in a second alternative embodiment. In FIG. 7 , H ¹ =4 and M ¹ =2. Figure 7 is similar to Figures 5 and 6 in many respects. Messages 501a and 501b are examples of Report 1, which includes a rank indicator (RI) and a 1-bit PTI value=1. Similarly, messages 503a, 503b, and 503c are examples of report 3, which includes a subband precoder matrix value SBW2 and a subband channel quality indicator (SBCQI) value. However, messages 701a and 701b are new. Messages 701a and 701b are examples of report 2. Since PTI=1, messages 701a and 701b include wideband W1 and wideband CQI.

In a third alternative embodiment (ALT3), W1 information is reported in report 2 when PTI=1. Therefore, Report 1 includes RI and 1 bit of Precoder Type Indication (PTI). In report 2, if PTI=0, report W1. If PTI=1, report W1. In report 3, if PTI=0, wideband CQI and wideband W2 are reported. If PTI=1, subband CQI and subband W2 are reported. A third alternative embodiment is depicted in FIG. 8 .

Figure 8 shows a modified feedback report with a precoder type indicator (PTI) value of 1 in a third alternative embodiment. In FIG. 8, H ¹ =4 and M ¹ =2. Figure 8 is similar in many respects to Figures 5-7. Messages 501a and 501b are examples of Report 1, which includes a rank indicator (RI) and a 1-bit PTI value=1. Similarly, messages 503a, 503b, and 503c are examples of report 3, which includes a subband precoder matrix value SBW2 and a subband channel quality indicator (SBCQI) value. However, messages 801a and 801b are new. Messages 801a and 801b are examples of report 2. Since PTI=1, messages 801a and 801b include wideband W1.

In yet another embodiment of the present disclosure, when PTI=1, a new report is added. Therefore, there will be four reports in this CSI mode. However, the precoder W is determined from the 3-subframe report conditional on the last Rank Indicator (RI) value transmitted. Therefore, Report 1 includes RI and 1 bit of Precoder Type Indication (PTI). In Report 2, W1 is reported if PTI=0, and W1 is reported if PTI=1 (similar to Figure 8). In report 3, if PTI=0, wideband CQI and wideband W2 are reported, and if PTI=1, wideband CQI and wideband W2 are reported. In report 4, if PTI=0, there is no report. If PTI=1, subband CQI and subband W2 are reported.

In this way, PTI is used to turn on/off subband CQI reporting, and report 4 (subband CQI/W2) is reported only when PTI=1. This alternative embodiment is depicted in FIG. 9 .

FIG. 9 shows a modified feedback report with a precoder type indicator (PTI) value of 1 in which 4 report types are used. Figure 9 is similar in many respects to Figures 5-8. Messages 501a and 501b are examples of Report 1, which includes a rank indicator (RI) and a 1-bit PTI value=1. Messages 801a and 801b are examples of report 2. Since PTI=1, messages 801a and 801b include wideband W1. Similarly, messages 503a and 503b are examples of report 3, which includes SBW2 and SBCQI.

However, messages 901a and 901b are new. Messages 901a and 901b are examples of report 4. Since PTI=1, messages 901a and 901b include subband CQI and subband W2. If PTI is 0, no 4 is reported.

In an advantageous embodiment of the present disclosure, when PTI=1, the feedback period of report 2 and report 3 is the same, and the following conditions hold:

N _P2 = N _P3 ;

H=N _P2 /N _P4 =J*K+2; and

M=N _P1 /N _P2 .

According to the codebook agreement in the document No.R1-105011 and the Chairman's note (Chairman's note), the payload for W2 is listed as follows: rank 1 = 4 bits, rank 2 = 4 bits, rank 3 = 4 bits, rank 4=3 bits. When PTI=1, the bit width of report 3 is shown in Table 1.

[Table 1]

rank W2 CQI L bit subband indication total payload rank 1 4 bits 4 bits 1-2 bits according to BW 10 Rank 2 4 bits 4+3 bits 1-2 bits according to BW 13 Rank 3 4 bits 4+3 bits 1-2 bits according to BW 13 Rank 4 3 bits 4+3 bits 1-2 bits according to BW 12 Rank 5-8 0 bit 4+3 bits 1-2 bits according to BW 9

However, it has been agreed that the payload of PUCCH format 2 should be limited to 11 bits. Therefore, as shown in Table 1, for rank 2 (13 bits), rank 3 (13 bits) and rank 4 (12 bits), the bit width of the current payload of PUCCH format 2 cannot accommodate (accommodate) in Table 1 Both the subband W2 of , the subband CQI and a bandwidth (BP) indication of L bits.

In an embodiment of the present disclosure, the L-bit subband indicator in the Rel-8 subband CQI feedback is reserved. However, the following alternatives are used to limit the payload of subband feedback to within 11 bits.

Alt 1 : In CSI Mode 1, codebook subset selection (codebook subsampling) is performed on subband W2. That is, the W2 codebook (C2) used for subband feedback in PUCCH feedback is a subset of the W2 codebook used for wideband feedback in PUCCH feedback. For example, when PTI=1, C2 of W2 is a subset of C2 of W2 when PTI=0 in PUCCH feedback. In addition, C2 of W2 in PUCCH feedback when PTI=1 is a subset of C2 of W2 in PUSCH feedback. Table 2 shows the payload of subband CQI feedback in CSI Mode 1 for an example where C2 is subsampled and the payload of C2 for subsampling is 2 bits.

[Table 2]

rank W2 CQI L bit subband indication total payload rank 1 2 bits 4 bits 1-2 bits according to BW 8 Rank 2 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 3 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 4 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 5-8 0 bit 4+3 bits 1-2 bits according to BW 9

Alt 1 : When PTI=1, perform rank-dependent codebook subset selection (codebook subsampling) for subband W2 feedback. For example, the rank 2/3/4 codebook of W2 when PTI=1 is a subset of W2 when PTI=0 in PUCCH feedback. Furthermore, the rank 2/3/4 codebook of W2 when PTI=1 in PUCCH feedback is a subset of W2 in PUSCH feedback. Table 3 shows the payload of subband CQI feedback in CSI mode 1 for an example where C2 is subsampled and the payload for subsampled C2 is 2 bits for rank 2/3/4.

[table 3]

rank W2 CQI L bit subband indication total payload rank 1 4 bits 4 bits 1-2 bits according to BW 10 Rank 2 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 3 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 4 2 bits 4+3 bits 1-2 bits according to BW 11 Rank 5-8 0 bit 4+3 bits 1-2 bits according to BW 9

In another embodiment of the present disclosure, L bits of subband indication are removed for all ranks. Furthermore, between every two consecutive Report 2 instances, the remaining H-1 or H-2 (depending on whether wideband W2 and wideband CQI are reported separately from W1 ) reporting instances are used sequentially for subband CQI/W2 reporting , to cycle through the bandwidth section along with the subbands within the bandwidth section. For example, when H=J*K+1, and wideband W2/CQI is sent together with W1, there are J*K(H-1) reporting instances between two consecutive reporting 2 feedback instances.

This disclosure proposes multiple orders to cycle through bandwidth parts and subbands within the corresponding bandwidth parts in a given subband reporting instance.

Alternative 1 : Between two consecutive report 2 feedbacks, use the remaining J*K(H-1) or J*K(H-2) reports sequentially for subband CQI/W2 reports on each subband instance. Fig. 10 shows a subband reporting example for subband CQI/W2 reporting according to a first alternative embodiment of the present disclosure. In Fig. 10, three bandwidth parts are shown, BP1, BP2 and BP3. The first three reporting instances sequentially pass through each of the three subbands of bandwidth part BP1. Then, the fourth reporting instance begins to sequence through bandwidth part BP2.

Alternative 2 : Between two consecutive report 2 feedbacks, use the remaining J*K(H-1) or J*K(H-2) for the subband CQI/W2 reporting sequence over K periods of the bandwidth part Report instance. In addition, within the ith period of the bandwidth part, the mobile station reports the bandwidth of the ith subband within each bandwidth part. Fig. 11 shows an example of subband reporting for subband CQI/W2 reporting according to a second alternative embodiment of the present disclosure. In Fig. 11, three bandwidth parts BP1, BP2 and BP3 are shown. The first three reporting instances sequentially pass through the first subband of each of bandwidth parts BP1, BP2 and BP3. Then, the fourth reporting instance starts sequentially through the second sub-band of each of the bandwidth parts BP1, BP2 and BP3.

Alternative 3 : Between two consecutive report 2 feedbacks, sequentially use the remaining J*K(H-1) or J*K(H-2 ) report instance. Furthermore, assuming that there are at most T=2 ^L subbands within each bandwidth section, within the ith period of the bandwidth section, the mobile station reports the bandwidth of the ith subband within each bandwidth section.

By way of example, the mapping between i and j shown in Table 4 for the K=4 and T=4 cases can be used.

[Table 4]

i j 1 1 2 T 3 2 4 T-1

In general, for k=1, 2, 3, . . . , if i=2*k-1, then j=k, and if i=2*k, then j=T-k+1.

FIG. 11 shows an example of subband reporting for subband CQI/W2 reporting according to a third alternative embodiment of the present disclosure.

In one embodiment of the present disclosure, the subband size within the bandwidth portion depends on the rank indicator. That is, there may be larger subband sizes for higher ranks. In addition, subband CQI/W2 feedback modes also depend on different ranks.

In one embodiment of the present disclosure, the L-bit subband indications for rank 2, 3, and 4 feedback may be removed, while the L-bit subband indications for rank 1 and rank 5-8 are reserved. Therefore, Table 5 shows the payload size for subband CQI feedback in a possible implementation of CSI Mode 1 . In one embodiment, RI and PTI may be jointly coded in CSI mode 1.

[table 5]

rank W2 CQI L bit subband indication total payload rank 1 4 bits 4 bits 1-2 bits according to BW 10 Rank 2 4 bits 4+3 bits 0 11 Rank 3 4 bits 4+3 bits 0 11 Rank 4 3 bits 4+3 bits 0 10 Rank 5-8 0 bit 4+3 bits 1-2 bits according to BW 9

Industrial applicability

Although the invention has been described using the exemplary embodiments, it suggests various changes and modifications to those skilled in the art. It is intended that the present invention cover such changes and modifications as fall within the scope of the appended claims.

Claims (8)

1. A mobile station for use in a wireless network, operable to send feedback reports to a base station of the wireless network, the feedback reports comprising a first feedback report, a second feedback report and a third feedback report, wherein the the first feedback report includes a precoder type indication (PTI) value, and wherein at least one of the period of the second feedback report and the period of the third feedback report is indicated by the PTI value, Wherein, the second feedback report and the third feedback report include at least one of wideband feedback information and subband feedback information. 2. The mobile station according to claim 1, wherein if the PTI value is 0, at least one of the period of the second feedback report and the period of the third feedback report is determined by a higher layer message , and if the PTI value is 1, at least one of the period of the second feedback report and the period of the third feedback report is determined by J*K+1, where J is the number of bandwidth parts , and K is a constant signaled through a high-level message. 3. A method for use in a mobile station operable to send feedback reports to a base station of a wireless network, the method comprising: sending a first feedback report including a precoder type indication (PTI) value to the base station; sending a second feedback report to the base station; and sending a third feedback report to the base station, Wherein, the PTI value indicates at least one of the period of the second feedback report and the period of the third feedback report, Wherein, the second feedback report and the third feedback report include at least one of wideband feedback information and subband feedback information. 4. The method according to claim 3, wherein if the PTI value is 0, at least one of the period of the second feedback report and the period of the third feedback report is determined by a high layer message , and if the PTI value is 1, at least one of the period of the second feedback report and the period of the third feedback report is determined by J*K+1, where J is the number of bandwidth parts, And K is a constant signaled by a high layer message. 5. A base station for use in a wireless network operable to receive feedback reports sent by a mobile station, said feedback reports comprising a first feedback report, a second feedback report and a third feedback report, wherein said first a feedback report includes a precoder type indication (PTI) value, and wherein at least one of a period of the second feedback report and a period of the third feedback report is indicated by the PTI value, Wherein, the second feedback report and the third feedback report include at least one of wideband feedback information and subband feedback information. 6. The base station according to claim 5, wherein, if the PTI value is 0, at least one of the period of the second feedback report and the period of the third feedback report is determined by a high layer message , and if the PTI value is 1, at least one of the period of the second feedback report and the period of the third feedback report is determined by J*K+1, where J is the number of bandwidth parts, And K is a constant signaled by a high layer message. 7. A method for use in a base station of a wireless network operable to receive feedback reports sent by mobile stations, the method comprising: receiving a first feedback report; identifying a precoder type indicator (PTI) value in said first feedback report; determining at least one of the period of the second feedback report and the period of the third feedback report according to the PTI value; receiving the second feedback report; and receiving said third feedback report, Wherein, the second feedback report and the third feedback report include at least one of wideband feedback information and subband feedback information. 8. The method according to claim 7, wherein if the PTI value is 0, at least one of the period of the second feedback report and the period of the third feedback report is determined by a high layer message , and if the PTI value is 1, at least one of the period of the second feedback report and the period of the third feedback report is determined by J*K+1, where J is the number of bandwidth parts, And K is a constant signaled by a high layer message.